The Simple Hammer Test

Want a simple test to find out if a steel tank is rust-free? The Compressed Gas Association still recommends an oldtime method, the hammer test. It’s as simple as it sounds: hit the sidewall of an empty, unpressurized tank “with a light blow using a half-pound ball-peen hammer or equivalent,” and if the sound you hear is a clear bell tone, the tank is clean and free of corrosion. If the sound is dull or dead, however, suspect contamination with fluid, corrosion, or other foreign material and have the tank inspected. Also, bear in mind that the test is not effective on aluminum tanks.